Electrical protective device



1,563,399 Dec 1925 r-'. E. RICKETTS ELECTRICAL PRDTECTIVE DEVICE Filed se t. 24. 1920 2 Sheets-Sheet 1 WITNESSES: 5 INVENTOR 15/ 07 M Forfeit Z. iZ/ckc-ZZJ ATTORNEY Dec. 1 1925.

FIE. RICKETTS ELECTRICAL PROTECTIVE DEVICE Filed Sept. 24, 1920 2 Sheets-Sheet 2 AAA ATTORNEY WITNESSES: INVENTOR Patented Dec. 1, 1925.

UNITED STATES" PATENT OFFICE.

FORREST E RICKETTS, OF CATONSVILLE, MARYLAND.

ELECTRICAL PROTECTIVE DEVICE.

Application filed September 24, 1920. Serial No. 412,546.

To all whom it may concern: v 7

.Be it known that I, FORREST E. RICKETTS,

a citizen of the United States, and a resident of Catonsville, in the county of Baltimore and State of Maryland, have invented a new and useful Improvement in Electrical Protective Devices, of which the following .is a specification.

My invention relates to electrical protec: tive devices and particularly to means for protecting parallelconn'ected transmission circuits.

One object of my invention is to provide effective means for selectively protecting parallel-connected conduetors. A

Another object of my invention is to provide means for so decreasing the time elements of protective relays associated" with faulty feeder circuits that the faulty circuits may be isolated before normal parallel-conne'cted circuits become affected by the same fault.

Another object of. my invention is to pro- L that is normally maintained in a relay by a saturable torque-compensatin transformer, by short-circultlng the trans ormer.

317,651, filed August 15, 1919, I disclose a selective balance relay that is employed for protecting parallel-connected transmission circuits in co-operation with the usual overload relay. The balance relay is energized through current transformers, from each of i the parallel-connecte circuits and is adapt- ,f ed to select either circuit, when a fault 0c} curs therein, and to instantaneously tri the circuit interrupters of that circuit. mall pallet switches, that are actuated by the respective circuit interrupters, short-circuit the selective relay and theoverload relay at the correspondin ends of the fault circuit to prevent imm Ina co-pending application, Serial No.

iate actuation of t e inter-v unbalanced energization of the selective relay. The normal circuit remains in operation and retains its ordinary overload pro tection, with a predetermined time element in the operation of its relays, depending upon the value of the overload current.

- United States Patent No. 1,286,239, issued Dec. 3, 1918, to A. W. Copley and B. H. Smith and assigned to the Westinghouse Electric & Manufacturing Company, discloses an induction-type protective relay embodying a torque regulator. The object of the torqhe regulator is to introduce a time element in the operation of the relay and to prevent, thereby, the instantaneous operation of the circuit interrupters upon the occurrence of a short-circuit or sudden heavy overload.

Thetorque regulator comprises an easily saturable current transformer connected between the circuit and the energizing winding of the relay. Beyond a certain value of circuit current, the current that traverses the secondary winding of the saturable transformer and the energizing winding of the relay remains substantially constant because of the saturation of the transformer. A time element is thus maintained irrespective of short-circuit currents of excessive values in the main circuit.

In the distributing systems heretofore eni- )lO ed re ressive time elements have been required in the relays employed in successive sections forjprotecting the apparatus connected to the-system. In many instances, the progressive settings have" necessitated an extremely large time setting-in the relays at.

the generating station. c

As stated above, one of the objects of the presentinvention is to obviate the necessity rupter in the normal circuit because of an 1n my co-pendingapplication, in co-operation with the time-element protective relays,

that are disclosed. in the above-mentioned patent, to provide effective means for selec- In practicing my invention, I provide protective relays that embody the'torque regulator for protecting theparallel-connected circuits. The differential relay is so disposed that, upon an occurrence of a fault in either circuit, its contacts will select the relay or relays that protect the'faulty circuit. I provide, further, an auxiliary switch or rela the setting of which may be so adjusted t at it will be actuated only when the circuit current attains a predetermined value. This relay, when actuated by the current of predetermined value, co-operates with the contact members of the diflerential, or selective, relay to short-circuit the torque regulator of the overload relay that is connected to the faulty circuit. The time element that is normally maintained by the torque regulator of the overload protective relay is thus decreased to about one-half the predetermined normal value.

The employment of the auxiliary switch, or relay, obviates the necessity for the additional pallet switch on the circuit interrupter and, since it may be disposed adjacent the differential or selective relay, effects considerable saving in wire which would, otherwise, be required for the connections between the palletswitch on the circuit interrupter and the terminals of the differential rela The use of the auxiliary relay, in combination with the differential relay also precludes the actuation of the differential relay upon the occurrence of surges in the circuit and also obviates the necessity for providing an exact balance in the current-transformer circuits. The differential relay may thus be made extremely sens'tive without the disadvantages of requiring exact balances inthe current transformers and of operating upon the occurrences of surges in the cirouits.

The actual isolation of a circuit is thus made dependent upon the current in that circuit attaining a predetermined value and maintaining that value for a redetermined interval of time. The reduction of the interval of time required to isolate the faulty circuit, below the value of time required for the actuatiofi of the circuit interrupters in the normal circuit, insures isolation of the faulty circuit only. With this arrangement, only relays that are responsive to current are necessary, and the expense incidental to supplying a plurality of potential transformers 1s obvlated.

In the accompanying drawings,

Figures 1, 3 and 4 are diagrammatic views of electrical distributing systems embodying my invention; and 4 Fig. 2 is a diagrammatic view of a selective relay system embodying my invention. Generator bus bars 1 and 2 are connected to substation bus bars 3 and4 through two parallel-connected feeder circuits 5 and 6.

Circuit interrupters 7 and 8 are connected in the conductors 9 and 10, of the circuit 5, at the respective ends thereof. Circuit interrupters 11 and 12 are connected in conductors 13 and 14, of the circuit 6, at the respective ends thereof. Series transformers l5 and 16 are so disposed with respect to the circuit 5 as to have current induced therein that shall be proportional to the current traversing the two ends of the circuit 5. Similarly, transformers 17 and 18 are connected at the respective ends of the circuit 6. The transformers 15 and 17 are connected by an auxiliary circuit 19, and the transformers 16 and 18 are connected by an auxiliary circuit 20.

Time-limit overload relays 21 and 22, construeted substantially as indicated in the patent referred to above, are connected to the transformers '15 and 17, respectively, for the purpose of controlling the tripping magnets 23 and 24 of the interrupters 7 and 11, respectively. The relays 25 and 26 are similarly connected to the current transformers 16 and 18 for the purpose of controlling the tripping magnets 27 and 28 of the interrupters 8 and 12, respectively. The overload relays 21, 22, 25 and 26 are adapted to complete the circuits through the respective tripping magnets controlled thereby, from auxiliary circuits and 80, respectively.

The time-limit overload relays 21, 22, 25 and 26 severally comprise a current transformer 29 havin a primary winding 29 and a secondary winding 30, a torque regulating saturable transformer 31 and a. winding 32 which co-operates' with the winding 30 to operate the relay.

The primary winding 29 of each relay is energized from the corresponding current transformer. The energization of the winding 32 is controlled by the saturable transformer 31 which comprises a primary winding 33 and a secondary winding 34. The primary winding 33 is energized directly in accordance with the value of the current that traverses the circuit 5 or the circuit 6 but the current induced in the secondary winding 34 is substantially constant because of the saturation of the regulating transformer 31 which is connected between the winding 30 and the winding 32.

When .the winding 32 is sufliciently energized for a predetermined interval of t me, engagement is effected between the contact members 35 and 35 of the relay.

A differential or selective relay 36 is employed with each set of overload relays at the respective ends of the parallel-connect ed conductors. The selective relay 36 comprises two windings 37 and 38. that are energized from the. current transformers of the parallel-connected conductors, and a third winding 39 that is connected between the juncturcs of the current transformer windings and of the windings 37 and 38 of the relay 36. The relay 36 further comprises a movable contact member 46 that is adapted .to engage either of two stationary contact members 41 and 42, depending upon the respective degree of energization of the windings 37 and 38.

Two auxiliary relays 43 and 44 are employed to co-operate with the contact members of the relay 36 to short-circuit the torque regulators 31 in the overload relays 21 and 22. Similarly, a ditierential relay 45 and two auxiliary relays 46 and 47 cooperate to short-circuit the torque regulators of the relays and 26. As the torque regulator is short-circuited, the winding 32 is energized in direct accordance with the yalue of the current traversing the. circuit and the time element, that is normally maintained by the torque regulator, is eliminated.

One terminal of the secondary winding of the current transformer 15 is connected to one terminal of the winding 29, of the relay 21, and the winding 48 of the auxiliary switch 43 is connected between the second terminal of the winding 29 and the free terminal of the winding 37 of therelay 36. The winding 49, of the auxiliary switch 44, is similarly connected between the free terminal of the. winding 38, of the selective relay 36, and one terminal of the winding 29 of the relay 22, the other terminal of winding 29 being connected to one terminal of the transformer 17. The other terminals of the -currentv transformers 15 and 17 are both connected to the freeterminal of the windselective relay 36.

ing 39 of the selective relay 36.

A terminal of the prnnary wlndmg 33 and a terminal. of the secondary winding 34 of .the torque regulator 31 are joined by a conductor 50. The other terminal of the winding 33, of the relay 21, is connected to a contact member 51, of the auxiliary relay 48, and the other terminal of the winding 34, of the. relay 31, is connected to the contact. member 41 of the selective relay 36. The contact members 52, of the auxiliary relays 43 and 44, are both connected to the movable contact. member of the selective relay 36. Similarly, one terminal of the winding 33, of the relay 22, is connected to terminal 51, 0f the auxiliary relay 44, and one terminal of winding 34 of the relay 22 is connected to the stationary contact member 42 of the The windings of the relays 25, 26, 45, 46 and 47 are similarly connected, through the current transformers 16 and 18, to the circuits 5 and 6. I

In a system elnployingan even number of circuits to distribute energy, the circuits may readily be grouped in pairs with a selective relay for each pair of circuits, at the respective ends thereof. In a system having an odd number of circuits, the circuits are grouped in pairs. and the odd circuit may be provided with ordinary overload protection, as is illustrated in Figs. 1 and 3.

In Fig. l. the odd circuit 53 is provided with circuit interrupters 54 and 55 at the respective ends thereof. Current transform ers 56 and 57 and overload relays 58 and 59 are provided atcorresponding ends of the circuit 53 for the purpose of controlling the tripping magnets 66 and 61 of the interruptcrs 54 and 55, respectively. The overload relays 58 and 59 are adapted to complete the circuits through the corresponding tripping magnets 60 and 61 controlled thereby. from the auxiliary circuits't'O'and 80. respectively.

The time interval of each of the overload relays 21, 22 and 58, since theyare adjacent the generator end of the circuits 5, 6 and 53, may be, for convenience, two seconds. The relays 25, 26 and 59 should, however, be adjusted for a smaller time interval and, for convenience, may be considered as having a time interval of one second each.

Similarly, such relays as might be disposed in successive sections, as illustrated in Figs. 3 and 4, for the protection of parallel-connected feeder circuits connected therein, would have corresponding time intervals of two seconds for the relays adjacent the power end of the circuits and of one second for the. relays adjacent the load end of the circuits.

A system having only two parallel-connected feeder circuits between the generator 62 and the substation bus-bars 63 may be provided with the differential relay protective system at each end of the feeder circuits if an additional source of energy 64 is available at the substation, as. in Fig. 4.

-' Where, however, no additional source of energy is available, a third feeder circuit should be provided to obtain a greater degree of protection, as in Fig. 1 or in the section shown in Fig. 3 between the first and the second substation bus-bars 63 and 65, respectively. i

If in Fig. 1 a fault should occur at the point X in the circuit 5, a current of reater value would traverse the current trans ormer 15 than the transformer 17 and the winding 3'? of the selective relay 36 would be energzed to a greater degree than the winding iiicted between the contact members 40 and Engagement would thereupon be ef- 120 When the value of the current traversing the transformer 15 attains a predetermined value, the auxiliary relay 43 operates to effect engagement between its contact members 51 and 52. A circuit is then completed from one terminal of the winding 33 in the relay 21 through the contact members 51 and 52 of the auxiliary relay 43 and the contact members 40 and 41 of the selective relay 36 terrupter 11.

The circuit interrupter 8 would similarly be tripped, through the action of its relay 25 and the differential relay 45, before the in-' terrupter 12 could be actuated, and the circuit 5 would be completely isolated.

The normal circuit 6 would continue in operation and, although the energization of the winding 38 of the differential relays 36 and 45 would eflect engagement between the contact members 40 and 42, the overload relays 22 and 26 would continue to operate normally because the setting of the auxiliary relays 44 and 47 would preclude the operation thereof until the current traversing the circuit 6 attained a predetermined value. The employment of the auxiliary switches 43 and 44 also precludes tripping of circuit interrupters upon the occurrence of surges in the circuits.

The desired time element in the overload relays is thus normally maintained for ordinary overload protection. The employment of the differential relay to short-circuit the compensators of the relays connected to a circuit wherein a fault occurs, serves to decrease the time element sufliciently to permit isolation of the faulty circuit before the interrupters of the parallel-connected circuit may be tripped.

My invention is not limited to the specific arrangement illustrated, as it may be variouslymodified without departing from the spirit and sec of the invention as set forth in the appen ed claims.

I claim as my invention:

1. In an electrical system of distribution, the combination with parallel-connected feeder conductors, of means having a time element and responslve to the current traversing the conductors and means for reducing the time element of the current responsive means comprising means responsive to an unbalance in the current traversing the parallel conductors.

2. In an electrical system of distribution, the combination with parallel-connected feeder conductors, of means having a time element and responsive to the current traversing the conductors, means responsive to an unbalance in the current traversing the parallel conductors for reducing the time ele-' ment .5. the current-responsive means, and

an unbalance in the current relations of theparallel-connected feeder conductors.

4. In an electrical system of distribution, the combination with parallel-connected feeder conductors, of means having a time element and responsive to the current traversing the conductors and a relay operative only when the currents traversing the conductors are unbalanced for reducing the time elements of the current-responsive means of only the circuit that is so affected as to cause an unbalance in the current relations of the parallel-connected feeder conductors. 5. In an electrical distribution system, the combination with a plurality of parallelconnected feeder conductors extending be tween two points of the system, of relays having a predetermined time element for disconnecting the conductors from the system, and relay controlling means for selecting and rendering the disconnecting relays of faulty feeder conductors operative and for simultaneously decreasing the predetermined time element to disconnect the faulty conductors before the normal parallel-connected conductors become disconnected from the system. o .6. In an electrical distribution system, the combination with a plurality of parallelconnected feeder conductors extending be tween two points of the system. of relays having a predetermined time element for disconnecting the conductors from the system, and selective means for decreasing the predetermined time element of the relay associated with a faulty feeder to disconnect the faulty conductors before the normal parallel-connected conductors become disconnected from the system.

7. In an electrical distribution system, the combination with a plurality of parallelconnected feeder conductors extending between two points of the system, of relays having a predetermined time element for disconnecting the conductors from the system upon occurrences of overload or shortcircuits on the feeder conductors, and selective means for rendering the disconnecting relays of a faulty feeder operative only upon the occurrence of a short-circuit thereon and for simultaneously decreasing the predetermined time element to disconnect the faulty conductors before the normal parallel-connected conductors become disconnectedfrom ,connected feeder con uctors extending between two points of the system, of relays having a predetermined time element for disconnecting the conductors from the system, and relay-controlling means for selecting the disconnecting relays of faulty feeder conductors and simultaneously decreasing the predetermined time element to disconnect the faulty conductors before the normal parallel-connected conductors become disconnected from the system.

9. In an electrical distribution system, the combination with a plurality of parallelconnected feeder conductors extending between two points of the system, of relays having a predetermined time element for disconnecting the conductors from the system, relay-controlling means for selectingthe disconnecting relays of the faulty feederconductors, and means responsive to a predetermined value of current in the faulty,

feeder for decreasing the predetermined time element to disconnect the faulty con-' ductors before the normal parallel-connected conductors become disconnected from the. system. V

10. In an electrical distribution system, the combination with a plurality of parallelconnected feeder conductors extending between two points of the system, of relays having a predetermined time element for disconnecting the conductors from the system, and means for decreasing the time element of the corresponding disconnecting relays to obtain a quick disconnectionof a faulty feeder conductor.

11. In an electrical distribution system, the combination with a plurality of parallelconnected feeder conductors extending between two points of the system, of relays having a predetermined time element for disconnecting the conductors from the systerm, a current transformer in each conductor for energizing the disconnecting relays, and

' means for selecting the corresponding relays of a faulty conductor and decreasing the predetermined time element thereof to disconnect the faulty conductors from the system before the normal parallel-connected conductors become disconnected from the system.

12. The combination with an induction relay and means or causing the time of operation thereof to be substantially constant, of means for neutralizing the effect of said timing means.

, conditions in the circuit.

, 13. The combination with an induction re lay and a torque regulating device for causing the time of operation thereof to be substantially constant, of means for neutralizing the effect of the torque regulating device.

14. The combination with an induction relay and a torque regulating device for causing the time of operation thereof to. be substantially constant, of a relay for neutralizin the eflect' of the torque regulator.

15. The combination with an induction relay and means for causing the time of operation thereof to be substantially constant, of

means-responsive to the current traversing the relay for neutralizing the effect of the timing means.

16. The combination with an induction relay and means for causing the time of operation thereof to .be substantially constant, of means responsive to a predetermined value of current traversing the relay for neutralizing the effect of the timing means.

17. The combination withan induction relay having means for controlling the time element thereof, of means for controlling the time-element controlling means in accordance with predetermined conditions.

.18. The combination with a circuit and an induction relay connected thereto having means for controlling the time element thereof, of means for" controlling the time-elementcontrolling means in accordance with the current in said circuit.

19. In an overload relay, the combination with an actuating winding and a Saturable transformer connected between the winding and the circuit to which the relay is connected, of means for short-circuiting the transformer under predetermined condi-, tions.

20. The combination with a circuit and an induction relay connected thereto having normally a definite-time characteristic when current in excess of a predetermined value traverses said circuit, of means for alterin said characteristic under predetermine 21. The combination wlth two parallel transmission circuits and a relay having a predetermined time characteristic for controlling one of said circuits, of means including a balanced device controlled by the currents in said circuits for altering said characteristic when a fault occurs in said one of said circuits.

In testimony whereof, I have hereunto subscribed my name this eighteenth day of September roaians'r n- RIOKETTS. 

